feat: add the ability to pause and resume jobs

[reugn]

Issue: #100

[codecov-commenter]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (7a5e12f) 89.49% compared to head (028b631) 90.41%.

Files	Patch %	Lines
quartz/scheduler.go	92.59%	2 Missing and 2 partials ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #102      +/-   ##
==========================================
+ Coverage   89.49%   90.41%   +0.91%     
==========================================
  Files          15       15              
  Lines         819      866      +47     
==========================================
+ Hits          733      783      +50     
+ Misses         59       54       -5     
- Partials       27       29       +2     

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